A polymer electrolyte fuel cell using a proton conductive solid polymer membrane operates at a low temperature in comparison to other types of fuel cells, for example, a solid oxide fuel cell or a molten carbonate fuel cell. For this reason, the polymer electrolyte fuel cell has been expected to be used as a power source for energy storage system or a driving power source for a vehicle such as a car, and practical uses thereof have been started.
In general, such a polymer electrolyte fuel cell uses expensive metal catalyst represented by platinum (Pt) or a Pt alloy, which leads to high cost of the fuel cell. Therefore, development of techniques capable of lowering the cost of the fuel cell by reducing a used amount of noble metal catalyst has been required.
For example, JP-A-2012-124001 (US 2013/244137 A1) discloses a catalyst for polymer electrolyte fuel cell having catalyst particles made of platinum supported on a carbon powder support. 0.7 to 3.0 mmol/g (in terms of support weight) of a hydrophilic group binds to the carbon powder support, the platinum particle has an average particle diameter of 3.5 to 8.0 nm, and a specific surface area (COMSA) of platinum by CO adsorption is in the range of 40 to 100 m2/g. JP-A-2012-124001 (US 2013/244137 A1) discloses that initial activity (initial power generation characteristic) can be secured by introducing the hydrophilic group into the platinum catalyst which wettability has been degraded by an annealing process to make a functional group disappear from the surface of support.